Rotor System

Question 1

NATOPS Chap 2

Rotor System

What type of Rotor system do we have?

Answer 1

A fully articulated rotor system

Question 2

NATOPS Chap 2

Rotor System

What are the four subsystems?

Answer 2

Main rotor blades, hub, flight controls, and bifilar vibration absorber.

Question 3

NATOPS Chap 2

Rotor System

How are the rotor blades attached to the hub

Answer 3

They are attached to hinged spindles and are retained by elastomeric bearings contained in the hub

Question 4

NATOPS Chap 2

Rotor System

What do the elastomeric bearings do?

Answer 4

They enable the blades to flap, lead, lag, and permit the blade to move about its axis for pitch changes

Question 5

NATOPS Chap 2

Rotor System

How is the rotor controlled

Answer 5

Control is provided via hydraulic servos which move the control rods attached to the swashplate.

Question 6

NATOPS Chap 2

Rotor System

How is the main rotor head supported

Answer 6

Via the shaft extension. The shaft extension is secured in place to the main shaft via the main rotor nut and the low pressure plate. The low pressure plate also provides an attachment for the swashplate assembly

Question 7

NATOPS Chap 2

Rotor System

How does the swashplate affect control inputs to the blades?

Answer 7

The swashplate slides around the main rotor shaft and tilts in the direction of the flight controls on a Teflon- coated uniball. Four pitch rods extend from the swashplate and connect to pitch change horns on the spindle. The pitch control rods transmit all movement of the flight controls from the sqashplate to the main rotor blades. Each rod is ground-adjustable for blade tracking

Question 8

NATOPS Chap 2

Rotor System

What do droop stops and flap restraints prevent?

Answer 8

They prevent extreme high or low blade flapping at low Nr

Question 9

NATOPS Chap 2

Rotor System

At what Nr do flap restraints permit coning?

Answer 9

At 35% Nr or greater, centrifugal force pulls out the restraints to allow coning and flapping of the blades

Question 10

NATOPS Chap 2

Rotor System

When do droop stops come out and in?

Answer 10

70% Nr and 50% Nr

Question 11

NATOPS Chap 2

Rotor System

Main Rotor Blades have….

Answer 11

“A pressurized hollow spar, honecomb core, outer skin, abraasion strips, electrothermal deicing mats, and a removable swept-back blade tip fairing”

Question 12

NATOPS Chap 2

Rotor System

What do the swept tips provide?

Answer 12

The 20* swept tips provide sound attenuation and rotor blade efficiency

Question 13

NATOPS Chap 2

Rotor System

Tail rotor system is…

Answer 13

“A bearingless, crossbeam tail rotor blade system which provides antitorque action and direction control

Question 14

NATOPS Chap 2

Rotor System

Where is the Tail Rotor and what does it provide?

Answer 14

On the right side of the Tail pylon, and it provides 2.5% lift in a hover due to the tail canted 20* upward

Question 15

NATOPS Chap 2

Rotor System

What does the tail rotor indexing system provide

Answer 15

It prevents the Tail Rotor from windmilling in winds up to 60kts

Question 16

NATOPS Chap 2

Rotor System

The Tail rotor head consists of..

Answer 16

Two plates. The inboard plat forms a hub, that is attached to the gearbox output shaft and retained by a shaft nut. The hub plates absorb axial thrust loads and bending moments and transmit torque to the tail rotor blades.

Question 17

NATOPS Chap 2

Rotor System

Gust Lock Caution(s)

Answer 17

When locking the gust lock, the switch shall be held in the LKD/UNLK position for a minimum of 5 sec to enable the actuator mechanism to complete its cycle.

Should rotor brake hyd pressure bleed off in a folded condition, the gust lock will not prevent the rotor brake disk from turning

Question 18

NATOPS Chap 2

Rotor System

What does AVCS do?

Answer 18

“Attenuates the magnitude and reduces the duration of the peak vibratory loads produced by the main rotor blade passage vibration frequency.”

Question 19

NATOPS Chap 2

Rotor System

What is used to provide a reference signal to allow AVCS to track changes?

Answer 19

The Nr tachometer

Question 20

NATOPS Chap 2

Rotor System

How many accelerometers/force generators are there?

Answer 20

The AVCS system uses 10 accelerometers and 5 force generators

Question 21

NATOPS Chap 2

Rotor System

When should the AVICS BIT be performed

Answer 21

Shall only be initiated with rotors static to avoid damage to dynamic components

Question 22

NATOPS Chap 2

Rotor System

Where are the main dampers installed, and what is their job?

Answer 22

They are installed between each of the main rotor spindle modules and the hub to restrain lead and lag motion of the main rotor blades during roation and to absorb rotor head starting loads. Each damper is supplied with nitrogen-pressurized hydraulic fluid form a reservoir mounted inside the main rotor shaft

Question 23

NATOPS Chap 2

Rotor System

Where is the Tail Rotor Quadrant, and what triggers the TAIL QUADRANT caution?

Answer 23

The tail rotor quadrant is mounted on the tail gearbox and transmits tail rotor cable movements into the tail rotor servo. Two spring cylinders are connected to the quadrant. In the event a cable is broken, the quadrant will operate normally by controlling the remaining cable against spring tension. The related microswitch mounted on the quadrant will illuminate the TAIL QUADRANT caution

Question 24

NATOPS Chap 2

Rotor System

What is the AVCS cycle?

Answer 24

It continuously analyzes aircraft vibrations and resets its vibration-nulling solution on a 300 seceond (5 min) cycle.